Gas dispersion is one of the key factors in the mineral flotation process. It can be expressed by many variables such as bubble size, gas holdup, gas superficial velocity and bubble surface area flux (S-b), In particular, Sb has been found to have a strong correlation with the flotation rate constant (K). Bubble size is important because it is related with the transport capacity and with the flotation probability. It also affects the gas holdup and the bubble surface area flux. In this work bubble sizes are measured using image analysis. An empirical rate constant model is developed to relate K with Sb and other dispersion variables. This model is found to be able to predict K for two different batch flotation cells.